Dismountable spark plug



Feb; 26 1924# H. KOERBER DIsMoUN'rALn SPARK PLUG Filed April 14 1923 Patented Feb. 26, 192.4.`

UNITED STATES 1,485,275 PATENT OFFICE.

HERMANN KOERBER, 0F STUTTGART, GERMANY, ASSIGNOR T0 ROBERT BOSCH AK- TIENGESELLSCHAFT, 0F STUTTGART, GERMANY.

DISMOUNTABLE SPARK PLUG.

Application led April 14, 1923. Serial No. 632,153.

To all vwhom t may concern.'

Be it known that I, HERMANN KOERBER, citizen of Germany, residing at Stuttgart, Germany, have invented certain new and useful Improvements in a Dismountable Spark Plug: and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In dismountable spark-plugs frequently an insulating body is used, having an expanded portion, which latter is arrangedy within a metal socket with the interposition of packing material. With the upper shoulder of this expanded portion or of the metal socket respectively engages the screwcap, which serves for securlng the insulating body within the spark-plug. When such a spark-plug has been repeatedly dismounted and reassembled, the tightness between the insulating body and the metal-socket is impaired for the reason, that, already at the first assembling of the spark-plug, the packing rings between the insulating body and the metal-socket are compressed somewhat, that means, said rings suffer a permanent reduction of their thickness. When the spark-plug is repeatedly reassembled, a progressive compression ,of the packingrings can not take place, as the metal socket,

surrounding the expanded portion of the insulating body, does not yield sufficiently in its longitudinal direction. After a repeated dismounting and re-assembling of the sparkplug, it may even happen, that the insulating body turns in its metal-socket, even when the screw-cap is screwed home. this character is of course entirely untight and accordingly useless.

According to the present invention this drawback is obviated thereby, that the metal-.socket is made resilient in longitudinal direction, so that its length can be reduced in conformance to the compression of the packing material between the insulating body and the metal-socket. The resiliency of the metal-socket is suitably produced in such a manner, that the wall of said socket for a part of its hei ht or length is weakened, so that it can old at a pressure, executed in longitudinal direction, or the wall can be rovideddirectly with transverse folds, ingentations or corrugations.

In the accompanying drawing, in which A plug of one form of construction of my improved spark-plug is illustrated,

Fig. l shows the spark-plug in longitudinal section and Figs. 2 and 3 vshow also in longitudinal section a detail of Construction in different positions.

The insulating Vbody l, in which the central electrode 2 is secured in the known manner, is provided with an expanded portion 3, which latter is enclosed by a metal-socket 4. Between the shoulders of the expanded portion 8 and the edges of the metal-socket packing-rings 5 are arranged.

For securing the insulating body 1 with the metal-socket 4 within the body 6 of the spark-plug a screw-cap 7 is provided, which in a known manner engages with the upper shoulder of the metal-socket and presses the latter together with the insulating body against a corresponding shoulder 8 of the plug body 6.

According to the invention the metal socket 4 is weakened at the point 9 in such a manner, that, when a pressure is exerted in longitudinal direction, an indentation or fold may be formed at this point.

The necessity of this fold`may be clearly seen from the enlarged illustrations in Figs. 2 and 3. Fig. 2 illustrates the initial condition of the packing-ring 5, provided between the insulating body 1 and the metal-socket 4. The packing ring 5, which for instance.

may be of rectangular cross-section, engages only with two of its ed es the respective faces of the insulating ody and of the metal-socket. Accordingly a slight pressure will be suiiicient to produce a safe packing and the fold 9 of metal socket will remain nearly unchanged.

Vhen, however, the plug has been repeatedly dismounted and reassembled, the packing ring 5 will.have received approximately the form illustrated in Fig. 8. The distance of -the tightening faces of the metal-socket and of the insulating body is considerably reduced in comparison to the initial condition. (Fig. 2.) As the same'reduction takes place at the lower end of the socket 4, a remarkable diminution of the distance between the upper and the lower end of the socket is produced. This diminution of the socket is made possible only thereby, that the fold 9 yields, that means is compressed, as shown in Fig. 3. In this manner the necessary adhesion of the packing ring 5 to the tightening aces can be eiiected always.

The invention is also suitable or adapted for such spark-plugs, in which the screwcap 7 does not act directly upon the metalsocket, but by means of intermediate members. The cross-sectional form of the packing-rings is also of no importance, as any packing material, adapted to be used for the purpose in question, undergoes such a permanent and strong deformation, that the disadvantage, mentioned in the beginning of this specification, will make its appearance.

I claim:

1. A dismountable spark-plug, comprising in combination, an insulating body, a metal socket enclosing part of said insulating body, packing material provided between said insulating body and said metal socket, a plug body and a screw-cap for securing said insulating body in said plug body, said metal socket being made to yield in the longitudinal,direction of the plug.

2. A ldismountable spark-plug, comprising in combination, an insulating body, a metal socket enclosing part of said insulating body,A packing material provided between said insulating body and said metal socket, a plug body and a screw cap for securing said insulating body in said plug body, a part of the Wall of the metal socket being weakened in order to effect the yielding of the socket.

3. A dismountable spark-plug, comprising in combination, an insulating body, a metal socket enclosing part of said insulating body, packing Vmaterial provided between said insulating body-and said metal socket, a plug body and a screw cap for securing said insulating body in said plug body, a part of the side Wall of said metal socket being weakened or corrugated.

4. A dismountable spark-plug, comprising iu combination, an insulating body, a metal 'socket enclosing part of said insulating body. packing material provided between said insulating body and said metal socket, a plug body and a screw cap for securing said insulating body in said plug body, said metal-socket having at least one fold in its side Wall. i

In testimony whereof I have hereunto affixed my signature.

HERMANN KOERBER. 

